The present invention relates to the fabrication of fiber reinforced plastic grates, and similar articles. In another aspect, the present invention relates to a process for producing fiber reinforced grating on a continuous basis. In a further aspect, the present invention relates to an apparatus for the continuous production of fiber reinforced elongated structures having nonuniform cross sections along the length thereof. In a still further aspect, the present invention relates to fiber reinforced plastic grating articles having a cross-sectional configuration and arrangement of fibers within the plastic which provides for increased strength and reduced usage of plastic resin materials. The present invention also relates to the fabrication of channels, bars and other open structural shapes of fiber reinforced plastic.
Corrosion resistant, electrically nonconductive grate articles have many applications including, for example, catwalks, flooring, and the like, in industrial environments where chemical corrosion or high power electrical equipment and lines make conventional metallic grating articles undesirable, or unsafe. The term "grating articles" as employed herein refers to any structure having longitudinal span members running substantially parallel to one another and interconnected by transverse tie members, also spaced parallel to one another, so as to form a grid-like structure. Such structures can also include a bottom panel or sheet thereby forming a grate-like structure having five sided cells.
Grating materials having anticorrosion and nonconductive properties are considered by coating conventional metallic grid structures with noncorrosive or nonconductive materials or by fabricating plastic resins, reinforced with fibrous materials, into grate structures. It is to the latter type of grate articles that the present invention is directed.
Until recently, fiber reinforced grate structures were manufactured on a batch basis normally employing open faced molds. Basically, conventional fiber reinforced grates are produced by pouring thermosetting plastic resin materials into the mold, filling the grooves therein. Next, reinforcing fibers are manually or machine laced into the grooves of the open-faced grating mold which, depending upon the configuration of the grating structure, can resemble a waffle iron pattern, for example. The entire open-faced mold is then heated causing the thermosetting plastic to set, resulting in a fiber reinforced grate structure having the dimensions of the open-faced mold in which it was produced. The fiber reinforced grating is then removed from the mold and the process is repeated to obtain a second fiber reinforced plastic grate structure. This batch type production process has many inefficiencies, a major one of which is the fact that labor costs involved are fairly high because of the manual lacing of the reinforcing fibers and the necessity to produce the grate structures one at a time on a batch basis, allowing for the curing of the plastic resin materials before the mold can be refilled and the process repeated.
Another disadvantage attending fiber reinforced plastic grate structures produced in the past is that fairly large amounts of relatively expensive plastic resin must be employed in order to attain the strength and rigidity characteristics required in various applications of the grate structure. Generally, the cross section configuration of the span members and transverse tie members is rectangular, in order that the finished grate structure can be easily lifted from the open-faced mold. Such cross-sectional configurations do not provide for the most efficient structural use of the resin material. Further, because reinforcing fibers are laid into the vertically disposed grooves of the open-face mold, manual pressing of the fibers may result in an uneven distribution of fibers across the cross section of resulting grate structures.
Thus, a more economical and efficient process for producing fiber reinforced plastic grate structures on a continuous basis, rather than on a batch basis as described above, is desirable. Furthermore, an improved fiber reinforced plastic grate article providing greater structural strength and rigidity, while reducing usage of expensive plastic resin materials, would be advantageous.